Simplify the following expression: $t = \dfrac{7z}{9} + \dfrac{-4z}{9}$
Answer: Since the expressions have the same denominator we simply combine the numerators: $t = \dfrac{7z - 4z}{9}$ Combine like terms: $t = \dfrac{3z}{9}$ Simplify by dividing numerator and denominator by 3: $t = \dfrac{z}{3}$